A variable delay element has proven to be a useful circuit element in many applications. For instance, a delay element is one of the key functional blocks in a delay-locked loop (DLL) circuit. A DLL circuit typically synchronizes an internal clock with an incoming clock.
The variable delay element is also used in clock-and-data recovery (CDR) systems. In CDR systems, a clock and data are recovered from a single high-speed serial stream of non-return-to-zero (NRZ) data.